As a consequence of our efforts in the crystal growth laboratory we may be able to extend our conformational studies of the classical prostaglandin (PG) hormones to include PGF1 alpha, NaPGB2, ZnPGE1 and either PGD1 or PGD2. The PGF1 alpha study should clarify whether the alpha-chain ring junction geometry is trans planar to C9 as expected by comparison to other PG1 series structures, or trans planar to C12 as a consequence of the combined effects of the 9-alpha-hydroxyl and accute side chain ring torsional angle observed in other F series PG's. The PGD conformational study should reveal the influence, if any, of an 11 keto group on the delta 13 bond plane, ring junction geometry. The examination of a number of PG endoperoxide analogs should corroborate the previously observed destabilization of the peroxide bond as well as reveal the degree of deformation of the endoperoxide ring system afforded by side chains substituents, such as the chorine atoms in trans-4, 5-dichoro-1,2-dioxabicyclo(2,2,1) heptane. The collection and refinement of low temperature diffraction data for three previously determined, room temperature disordered structures should be a routine operation once the currently available liquid nitrogen temperature control apparatus has been tested. It may be possible to examine the conformation of 15(S)-methyl PGF2 alpha in underivatized form once the problems with crystal twinning have been mitigated. We hope to procure stable esters of the PG endoperoxide analogs as well as suitable quantities of prostacyclin analogs from other laboratories for future conformational studies. We shall continue our efforts to probe the structural patterns of PG's and related compounds in the hope of uncovering yet more correlations between molecular conformation and biological activity.